DOMXPath / DOM - 检查是否可以在DOM中找到该元素

Question

这是我的代码：     

$url = "http://www.sportsdirect.com/football-shirts/premier-league-football-shirts/arsenal-football-shirts";    

libxml_use_internal_errors(true); 
$doc = new DOMDocument();
$doc->loadHTMLFile($url);

$xpath = new DOMXpath($doc);

$n  = $xpath->query('//div[@class="s-producttext-top-wrapper"]');
$l  = $xpath->query('//div[@class="s-producttext-top-wrapper"]/a');
$p  = $xpath->query('//div[@class="s-largered"]');
$im  = $xpath->query('//a[@class="ProductImageList"]');
$ra = $xpath->query('//div[@class="s-producttext-review"]/div');

$nl = $xpath->query('//a[@class="swipeNumberClick"][last()]')->item(0)->C14N();

echo $nl;

如何检查$nl是否在DOM中找到元素？

提前致谢！

Answer 1

当XPath:query()返回DOMNodeList的实例时，您可以检查length属性，以检查是否找到了任何节点：

$nl = $xpath->query('//a[@class="swipeNumberClick"][last()]');
# or $nl->length > 0
if ($nl->length) {
    $nl = $nl->item(0)->C14N();
}